The present invention relates to a full type ball bearing for turbochargers for motor vehicle engines, etc.
With turbochargers, for example, for motor vehicle engines, investigations are under way for a change-over from the floating bearing employing floating metal and presently in use to the ball bearing (antifriction bearing) mainly for the purpose of improving the responsiveness in the range of low speeds.
Since turbochargers are used at a high temperature, under a great load and at a high speed of rotation, common ball bearings comprising inner and outer rings, balls and a retainer, if incorporated therein, encounter the problem of a shortened life. During the rise to a high speed, especially, lubrication of the retainer portion poses a problem, leading to a failure of the bearing in a short period of time. To overcome the problem encountered with the retainer portion, there is a need to finish the retainer with high precision or to subject the retainer to a special treatment such as silver plating. Accordingly, full type ball bearings appear useful for turbochargers, whereas with the conventional full type ball bearing wherein the balls are made of steel, the contact between the balls involves slippage because the balls move in directions totally opposite to each other, entailing depletion of the lubricant and leading to an early failure of the bearing. For this reason, the full type ball bearing is not in use although the bearing is thought favorable for use in turbochargers.